CN112612073B - A color filter capable of realizing ultra-wide color gamut and its structural parameter determination method - Google Patents

Abstract

The invention discloses a color filter capable of realizing an ultra-wide color gamut and a method for determining structural parameters of the color filter. The range of colors and saturation that can be created by transmission or reflection of existing plasmonic filters is very limited. The invention includes a substrate layer and a silver film. The substrate layer is made of SiO ₂ . A silver film overlies the base layer. A plurality of hollow microstructures are etched on the silver film. The hollow microstructure comprises a cross-shaped groove and four rectangular grooves. The four rectangular grooves are respectively connected with the four ends of the cross-shaped groove. Compared with the existing surface plasma filter, the color obtained by the invention can exceed the color space of sRGB, and a wider color gamut is obtained. Compared with the existing color filter based on surface plasmon resonance, the color filter has wider color gamut and higher saturation, and can provide richer colors and more vivid image quality.

Description

A color filter capable of realizing ultra-wide color gamut and its structural parameter determination method

technical field

The invention belongs to the technical field of modeling and simulation of color filter devices, in particular to a new color filter based on surface plasmon resonance and capable of obtaining an ultra-wide color gamut.

Background technique

A filter is a commonly used optical device that is typically used to transmit or reflect specific wavelengths of light to display a desired color. Filters are widely used in displays, imaging sensors, anti-counterfeiting technology, color decoration, color printing and other fields. Traditional filters use traditional dye tinting to absorb specific wavelengths of light to display a specific color. Such conventional chemically dyed filters cannot withstand high temperatures or UV radiation, and filter performance can degrade significantly over time. In order to solve the problems of traditional filters, filters based on structural color have appeared in recent years. Structural color is produced by the interaction between natural light and micro-nano structures, and usually occurs in optical phenomena such as interference, diffraction, and scattering. Compared with the color formed by chemical dyeing, structural color has the advantages of non-fading, color stability, and environmental protection. These advantages of structural color have led researchers to work on filters based on guided mode resonance, surface plasmon resonance, Mie resonance, or Fabry Perot resonance.

In practical applications, highly saturated structural colors and wide color gamut play a crucial role in display and imaging. In display or imaging, the higher the saturation, the more vivid the displayed colors, and the wider the color gamut, the more colors displayed. However, the color range and saturation formed by the transmission or reflection of light through existing plasmonic filters is very limited. The limited color range and saturation can cause the color of the light to pass through the filter to produce too few colors to achieve the desired effect. This defect can make the image quality after imaging too low, which limits the further application of plasmonic filters.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a color filter capable of realizing an ultra-wide color gamut, so as to utilize the incident white light to obtain an ultra-wide color gamut.

The present invention is a color filter capable of realizing ultra-wide color gamut, comprising a base layer and a silver film. The material of the base layer is SiO ₂ . A silver film covers the base layer. A plurality of hollow microstructures are etched on the silver film. The hollow microstructure consists of a cross-shaped groove and four rectangular grooves. The four rectangular slots are respectively connected with the four ends of the cross-shaped slot.

Preferably, the light transmission wavelength range of the filter can be adjusted by adjusting the length D of the rectangular groove.

Preferably, the hollowed-out microstructures are arranged in a matrix; the value range of the distance P between the center points of two adjacent hollowed-out microstructures is 150-300 nm.

Preferably, the thickness H of the silver film ranges from 40 to 100 nm.

Preferably, the value range of the length D of the rectangular groove is 20-80 nm;

Preferably, the hollow microstructure is centrosymmetric about the central point of the cross-shaped groove.

Preferably, the connection between the rectangular groove and the corresponding end of the cross-shaped groove is the middle position of the rectangular groove.

Preferably, the corresponding ends of the rectangular groove and the cross-shaped groove are perpendicular to each other.

Preferably, the cross-shaped groove is composed of two elongated grooves that are equally divided perpendicularly to each other.

The color filter capable of realizing ultra-wide color gamut and the method for determining its structure parameters, the specific steps are as follows:

Step 1: Determine the design requirements of the transparent filter. Design requirements include the target visible wavelength range and maximum light transmittance.

Step 2: Determine the thickness H of the silver film, the value of the center distance P of the adjacent hollow microstructures, and the length D of the rectangular groove according to the target visible light band range;

The target visible light band range and the green band range, blue band range, and red band range are compared as follows:

①. If the target visible light band has the highest degree of overlap with the green band, and the maximum transmittance is greater than or equal to 50%, select the silver film thickness H within the range of 40nm to 80nm; select the thickness H within the range of 150nm to 210nm. The center distance P of adjacent hollow microstructures is determined. The value range of the rectangular groove length D is set to be 20 nm to 80 nm.

②. If the target visible light band has the highest degree of overlap with the green band, and the maximum transmittance is less than 50%, select the silver film thickness H in the range of 90nm to 100nm; select the phase in the range of 210nm to 300nm. The center distance P of the adjacent hollow microstructures. The value range of the rectangular groove length D is set to be 20 nm to 80 nm.

③. If the target visible light band has the highest degree of overlap with the blue band, select the thickness H of the silver film within the range of 40nm-80nm; select the center distance P of the adjacent hollow microstructures within the range of 150nm-210nm. The value range of the rectangular groove length D is set to be 50 nm to 80 nm.

④. If the target visible light band has the highest degree of overlap with the red band, select the thickness H of the silver film in the range of 40nm-80nm; select the center distance P of the adjacent hollow microstructures in the range of 150nm-210nm. The value range of the rectangular groove length D is set to be 20 nm to 40 nm.

Step 3. In the value range of the rectangular slot length D determined in Step 2, take the maximum value as the rectangular slot length D, and gradually increase it; after each reduction, the filter of the current parameter is passed through the time domain finite difference. The method simulates the transmission spectrum until the simulated result meets the design requirements determined in step one.

Beneficial effects of the present invention:

In the present invention, a layer of silver film is plated on a silicon dioxide substrate, and a hollow microstructure composed of a cross-shaped groove and four rectangular grooves is etched on the silver film. Under normal incident light, the nanohole acts as a grating coupler to provide photon-plasmon momentum matching, enabling surface plasmon resonance to occur at the metal/dielectric interface. In this case, the plasma passes through the aperture and decays into radiation photons after passing through the metal thin film. By changing the size, shape, thickness, and period of the array, the allowable coupling frequency of the plasmonic elements can be tuned, and thus the color of the transmitted light. Compared with the existing surface plasmon filter, the color obtained by the filter can exceed the color space of sRGB and obtain a wider color gamut. Compared with existing surface plasmon resonance-based color filters, the filter has a wider color gamut and higher saturation, enabling richer colors and more vivid image quality.

Description of drawings

FIG. 1a is a schematic structural diagram of the present invention.

Figure 1b is a schematic diagram of a single hollow microstructure in the present invention;

Fig. 2a is the transmission spectrum diagram of transmission blue, green, red light under different parameters of the present invention;

Figure 2b is a coordinate diagram on the CIE1931 chromaticity diagram when blue, green and red light are transmitted under different parameters of the present invention;

Fig. 2c is the transmission spectrum diagram of the present invention when the size of D is adjusted under the condition of keeping P and H unchanged;

2d is a coordinate diagram on the CIE1931 chromaticity diagram when the size of D is adjusted while keeping P and H unchanged in the present invention;

Fig. 3a is the transmission spectrogram of the present invention when the size of H is adjusted under the condition of keeping P and D unchanged;

3b-3h are the coordinate diagrams on the CIE1931 chromaticity diagram when the size of D and H are adjusted while keeping P unchanged in the present invention;

Fig. 4a is the transmission spectrum when the present invention adjusts the size of P under the condition of keeping H and D unchanged;

4b-4q are coordinate diagrams on the CIE1931 chromaticity diagram when the size of D and P are adjusted while keeping H unchanged in the present invention.

Detailed ways

The present invention will be further described below with reference to the accompanying drawings.

As shown in Figures 1a and 1b, a color filter capable of realizing an ultra-wide color gamut includes a base layer 1 and a silver film 2. The material of the base layer 1 is SiO ₂ . The silver film 2 covers the base layer 1 . The thickness of the silver film 2 is H. A plurality of hollow microstructures 3 are etched on the silver film 2 . The hollowed-out microstructures 3 are arranged in a matrix; the distance between the center points of two adjacent hollowed-out microstructures 3 (ie, the structural period) is P. The hollow microstructure 3 includes a cross-shaped groove 3-1 and four rectangular grooves 3-2. The hollow microstructure 3 is center-symmetric about the center point of the cross-shaped groove 3-1. The cross-shaped groove 3-1 is composed of two elongated grooves intersecting vertically. The middle positions of the four rectangular grooves 3-2 are respectively connected with the four ends of the cross-shaped grooves 3-1. The rectangular slot 3-2 is perpendicular to the elongated slot connected to itself. The groove widths of the cross-shaped groove 3-1 and the rectangular groove 3-2 are both W. The length of the rectangular groove 3-2 is D; the length of a single elongated groove in the cross-shaped groove 3-1 (ie the distance between two opposite rectangular grooves 3-2) is L.

W=20nm; L=80nm; H=40～100nm; P=150～300nm; D=20～80nm.

By adjusting the size of the length D of the rectangular groove 3-2, the transmittance of the light in each wavelength band of the filter can be adjusted, thereby realizing the filtering of the light in different wavelength bands by the filter.

The color filter capable of realizing ultra-wide color gamut and the method for determining its structure parameters, the specific steps are as follows:

Step 1: Determine the design requirements of the transparent filter. Design requirements include the target visible light band range and the maximum transmittance of light in that band. The total wavelength range is 380nm～780nm, including the range of visible light red, green and blue bands and the maximum transmittance, of which the red band range is 640nm～780nm, the green band range is 500nm～550nm, and the blue band range is 420nm～500nm , in the visible light band range, the wavelength corresponding to the maximum light transmittance of the filter should be within the target visible light band range, the maximum light transmittance should be greater than 10%, the maximum light transmittance should be the peak value in this band, and This peak is the only peak within the band.

Step 2: Determine the values of H and P according to the target visible light band range;

Figures 3a and 4a only change the numerical transmittance of H and only change the numerical transmittance of P, respectively. The structural parameters of Figure 3a are P=200nm, D=80nm, H increases from 40nm to 100nm, step size is 10 nm, the structural parameters of Fig. 4a are H=80 nm, D=80 nm, P increases from 150 nm to 300 nm, and the step size is 10 nm.

It can be seen from the two figures that when the thickness H of the silver film 2 increases, the maximum transmittance decreases, and the resonance wavelength moves to the short-wave direction, and the transmittance is above 40%; when the period P increases, the maximum transmittance decreases. The rate is decreasing, and the resonant wavelength shifts toward the longer wavelength.

If you want to obtain light in the green band (500nm ~ 550nm), it can be intuitively seen from the two figures that the band ranges in the figures are basically in the green band, and the transmittance is required to be more than 50%. The thickness H of the silver film 2 can be set to 40nm～80nm, the period P can be set to 150nm～210nm; if the transmittance is less than 50%, the thickness H of the silver film 2 can be set to 90nm～100nm, and the period P can be set to 210nm～300nm;

If you want to obtain light in the blue band (420nm-500nm), it can be known from Figure 2c that with the change of the length D of the rectangular groove 3-2, the peak wavelength will gradually shift from the green band to the blue band, and the central transmittance will decrease, and the peak of the blue band will disappear after the length of D is reduced to 50nm, so we should make the transmittance of the filter as large as possible when the length of D is 80nm, the thickness of the silver film 2 H can be set to 40nm~80nm, period P can be set to 150nm~210nm, while the transmittance is high, the peak wavelength is more inclined to the blue band, so that when the transmittance exceeds 50% in the green band range, the peak wavelength shifts to the left The transmittance should be as large as possible when reaching the blue band;

If you want to obtain light in the red band (640nm-780nm), it can be known from Figure 2c that when the length D of the rectangular groove 3-2 is reduced to 20nm-40nm, the peak wavelength is just in the red band, and you want to obtain high transmittance The thickness H of the silver film 2 is set to be 40 nm to 80 nm, and the period P can be set to be 150 nm to 210 nm.

Step 3: The length D of the rectangular groove 3-2 is gradually increased from 80 nm; each time is decreased by 5 nm; after each decrease, the transmission spectrum of the filter with the current parameters is simulated by the finite difference time domain (FDTD) method, until The simulated results meet the design requirements determined in step 1.

In the following, the transmission spectrum of the nanostructure of the present invention is simulated by the finite difference time domain (FDTD) method to verify the difference of the filtering wavelength bands of the present invention with different parameters.

Spectral and Chromaticity Diagrams for Color Filters

By changing the thickness H of the silver film 2, the structural period P and the size of the four rectangular grooves 3-2D, three-color transmission spectra of red, green and blue can be obtained; as shown in Fig. 2a. In order to visually see the color rendering effect after filtering, the spectral data obtained by simulation are drawn on the CIE1931 chromaticity diagram, as shown in Figure 2b. As can be seen from these two figures, the structure we designed can realize red, green, and blue three-color filtering.

Specifically, in Figure 2a, the structural parameters corresponding to the blue spectral line are H=70nm, D=64nm, P=130nm; the structural parameters corresponding to the green spectral line are H=70nm, D=80nm, P=200nm; red The structural parameters corresponding to the spectral lines are H=70nm, D=20nm, P=200nm. Figure 2b shows the color coordinates corresponding to the red, green and blue spectral lines in the CIE1931 chromaticity diagram.

When the thickness H and the structural period P of the silver film 2 are determined (determined as P=200nm and H=80nm), only the length D of the rectangular groove 3-2 is reduced, the peak wavelength will be blue-shifted and the transmittance will be reduced, the second The peak wavelengths will appear in the red band. As shown in Fig. 2c, as the length D of the rectangular groove 3-2 decreases, the transmittance of the second peak wavelength will shift to the blue band. It shows that a relatively large range of colors can be obtained simply by reducing the length D of the rectangular grooves 3-2 from 80 nm to 20 nm in 10 nm steps. The corresponding colors of the transmission spectrum obtained after reducing the length D of the rectangular groove 3-2 from 80 nm to 20 nm were plotted on the CIE1931 chromaticity diagram, as shown in Fig. 2(d). After drawing the CIE1931 chromaticity diagram, it can be seen that by reducing the length D of the rectangular groove 3-2 from 80 nm to 20 nm, the black dots in Fig. 2(d) are distributed in a wide range, and a wide range of color gamut.

The influence of the thickness H of the simulated silver film 2 and the length D of the rectangular groove 3-2 on the filter characteristics

First, on the basis of changing the length D of the rectangular groove 3-2, we studied the effect of changing the thickness of the silver film 2 on the filter characteristics. The period was fixed at 200 nm, and the length D of the rectangular groove 3-2 was fixed at 80 nm. When the thickness of the silver film 2 is increased from 40 nm to 100 nm (the step size is 10 nm), the transmission spectrum shown in Fig. 3a can be obtained. When the thickness of the silver film 2 increases from 40 nm to 100 nm, the transmittance decreases and the transmission peak is blue-shifted. The full width at half-wave is also decreasing. Since a wide color gamut can be obtained by reducing the length D of the rectangular groove 3-2 from 80 nm to 20 nm, when a value is selected for the thickness of the silver film 2, the length D of the rectangular groove 3-2 is reduced from 80 nm to 20 nm. Therefore, each time the thickness of the silver film 2 is changed, the length D of the rectangular groove 3-2 is reduced from 80 nm to 20 nm, and the step size is 5 nm. The red triangle in the figure is the standard red, green, and blue color space (sRGB). The resulting transmission spectrum was then calculated to obtain the coordinates on the chromaticity diagram, and the color changes were marked on the CIE1931 chromaticity diagram, as shown in Fig. 3b–h. Figure 3b shows the change of the transmitted light band when P=200nm, H=20nm, and D decreases from 80nm to 20nm; Figure 3c shows the transmission when P=200nm, H=30nm, and D decreases from 80nm to 20nm The change of the optical band; Figure 3d shows the change of the transmitted light band when P=200nm, H=40nm, D decreases from 80nm to 20nm; Figure 3e shows P=200nm, H=50nm, D from 80nm The change of the transmitted light band when it is reduced to 20nm; Fig. 3f shows the change of the transmitted light band when P=200nm, H=60nm, and D decreases from 80nm to 20nm; Fig. 3g shows the change of the transmitted light band when P=200nm, H =70nm, the change of the transmitted light band when D decreases from 80nm to 20nm; Figure 3h shows the change of the transmitted light band when P=200nm, H=80nm, and D decreases from 80nm to 20nm;

When the thickness of silver film 2 is 60nm, the red light generated by the filter is closer to the center of the chromaticity diagram than the red light generated when the thickness of silver film 2 is 70nm or 80nm, resulting in lower saturation, as shown in Figure 3d-(f ) shown. When the thickness of the silver film 2 is 90nm or 100nm, the color gamut generated by the filter will shift to the upper left, and the blue light and red light generated by the filter are higher than the blue and red light generated when the thickness of the silver film 2 is 70nm and 80nm. Red light is closer to the center of the chromaticity diagram, again resulting in lower saturation, as shown in Fig. 3(e)-(h). When the thickness of the silver film 2 is 70nm or 80nm, the color range produced by the color filter can better match the range of the sRGB color space, thereby obtaining a wider color gamut. Low saturation results in fewer colors and a narrower gamut. Comparing the above seven figures, it can be concluded that when the thickness of the silver film 2 is 70 or 80 nm, a better color gamut range can be obtained. Except for the length D of the rectangular groove 3-2, the thickness of the silver film 2 also affects the color gamut. a factor.

Simulation of the influence of the structural period P and the length D of the rectangular groove 3-2 on the filter characteristics

In this part, on the basis of changing the length D of the rectangular groove 3-2, the influence of the filter period on the color rendering effect is discussed. Figure 4(a) shows the transmission spectrum when the filter period is increased from 150 nm to 300 nm when the thickness is constant. The thickness of the silver film 2 is 80 nm, and the length D of the rectangular groove 3-2 is 80 nm. It can be clearly seen from the figure that the smaller the period, the larger the transmittance and the larger the full width at half-wave. As the period increases, there will be a red shift in the peak wavelength. The length D of the rectangular grooves 3-2 was reduced from 80 nm to 20 nm in steps of 5 nm each time the size of the period was changed. The obtained transmission spectra were then calculated and the coordinates were plotted on the CIE1931 chromaticity diagram, as shown in Fig. 4b–q. Figure 4b shows the change of the transmitted light band when P=150nm, H=80nm, and D decreases from 80nm to 20nm; Figure 4c shows the transmission when P=160nm, H=80nm, and D decreases from 80nm to 20nm The change of the optical band; 4d shows the change of the transmitted light band when P=170nm, H=80nm, D decreases from 80nm to 20nm; Figure 4e shows the P=180nm, H=80nm, D decreases from 80nm The change of the transmitted light band when it is as small as 20 nm; Figure 4f shows the change of the transmitted light band when P=190nm, H=80nm, and D decreases from 80nm to 20nm; Figure 4g shows P=200nm, H= 80nm, the change of the transmitted light band when D decreases from 80nm to 20nm; Fig. 4h shows the change of the transmitted light band when P=210nm, H=80nm, and D decreases from 80nm to 20nm; Fig. 4i shows the change of the transmitted light band The change of the transmitted light band when P=220nm, H=80nm, D decreases from 80nm to 20nm; Figure 4j shows the change of the transmitted light band when P=230nm, H=80nm, D decreases from 80nm to 20nm ; Figure 4k shows the change of the transmitted light band when P=240nm, H=80nm, and D decreases from 80nm to 20nm; Figure 4l shows when P=250nm, H=80nm, and D decreases from 80nm to 20nm Changes in the transmitted light band; Figure 4m shows the change in the transmitted light band when P=260nm, H=80nm, and D decreases from 80nm to 20nm; Figure 4n shows P=270nm, H=80nm, D from The change of the transmitted light band when 80nm is reduced to 20nm; Fig. 4o shows the change of the transmitted light band when P=280nm, H=80nm, and D is reduced from 80nm to 20nm; The change of the transmitted light band when H=80nm, D decreases from 80nm to 20nm; Figure 4q shows the change of the transmitted light band when P=300nm, H=80nm, and D decreases from 80nm to 20nm.

As can be seen from the sixteen figures in Figures 4b-4q, the saturation of blue and red light obtained by the color filter does not change much with the increase of the period, while the change of green light is more pronounced. When the period size is in the range of 150nm-240nm or 280nm-300nm, it can be clearly seen that the green light obtained by the filter is in the color space of sRGB and is lower than when the period is in the range of 250nm to 270nm. The saturation of the green light generated by the detector is shown in Fig. 4(b)-(k) and Fig. 4(o)-(q). When the period size is in the range of 250nm-270nm, highly saturated green light can be obtained, and the overall color can exceed the range of the sRGB color space, resulting in a wider color gamut, as shown in Fig. 4(l)-(n) Show. Comparing the seventeen figures above, it can be concluded that when the period of the filter is in the range of 250nm-270nm, the obtained color range exceeds the sRGB color space, and a wider color gamut and higher saturation can be obtained. Besides the length D of the rectangular groove 3-2 and the thickness of the silver film 2, the size of the period is another major factor affecting the color gamut.

Claims (10)

1. A color filter capable of realizing ultra-wide color gamut comprises a substrate layer (1) and a silver film (2); the method is characterized in that: the silver film (2) is covered on the substrate layer (1); a plurality of hollow microstructures (3) are etched on the silver film (2); the hollow microstructure (3) comprises a cross-shaped groove (3-1) and four rectangular grooves (3-2); the four rectangular grooves (3-2) are respectively connected with the four ends of the cross-shaped groove (3-1).

2. A color filter enabling an ultra-wide color gamut as recited in claim 1, wherein: the light transmission waveband range of the filter is adjusted by adjusting the length D of the rectangular groove (3-2).

3. A color filter enabling an ultra-wide color gamut according to claim 1, wherein: each hollow-out microstructure (3) is arranged in a matrix shape; the value range of the central point distance P between two adjacent hollow microstructures (3) is 150-300 nm.

4. A color filter enabling an ultra-wide color gamut as recited in claim 1, wherein: the thickness H of the silver film (2) ranges from 40nm to 100 nm.

5. A color filter enabling an ultra-wide color gamut as recited in claim 1, wherein: the length D of the rectangular groove (3-2) ranges from 20nm to 80 nm.

6. A color filter enabling an ultra-wide color gamut as recited in claim 1, wherein: the hollow-out microstructures (3) are centrosymmetric about the central point of the cross-shaped groove (3-1).

7. A color filter enabling an ultra-wide color gamut according to claim 1, wherein: the connecting part of the corresponding end parts of the rectangular groove (3-2) and the cross-shaped groove (3-1) is the middle position of the rectangular groove (3-2).

8. A color filter enabling an ultra-wide color gamut as recited in claim 1, wherein: the rectangular groove (3-2) is perpendicular to the corresponding end part of the cross-shaped groove (3-1).

9. A color filter enabling an ultra-wide color gamut as recited in claim 1, wherein: the cross-shaped groove (3-1) is composed of two strip-shaped grooves which are vertically and equally divided.

10. A method of determining configuration parameters of a color filter enabling an ultra-wide color gamut as claimed in claim 3, characterized in that: step one, determining the design requirement of a transmission filter; the design requirements include a target visible band range and maximum transmittance;

secondly, determining the thickness H of the silver film, the numerical value of the center distance P of adjacent hollow microstructures and the length D of the rectangular groove according to the target visible light wave band range;

the target visible light wave band range is compared with the green wave band range, the blue wave band range and the red wave band range respectively as follows:

if the superposition degree of the target visible light wave band range and the green wave band range is the highest, and the maximum light transmittance is greater than or equal to 50%, selecting the thickness H of the silver film (2) in the range of 40 nm-80 nm; selecting the center distance P of the adjacent hollow microstructures (3) in the range of 150 nm-210 nm; setting the value range of the length D of the rectangular groove to be 20-80 nm;

if the coincidence degree of the target visible light wave band range and the green wave band range is highest and the maximum light transmittance is less than 50%, selecting the thickness H of the silver film (2) in the range of 90-100 nm; selecting the center distance P of the adjacent hollow microstructures (3) in the range of 210 nm-300 nm; setting the value range of the length D of the rectangular groove to be 20-80 nm;

selecting the thickness H of the silver film (2) in the range of 40 nm-80 nm if the overlapping degree of the target visible light wave band range and the blue wave band range is the highest; selecting the center distance P of the adjacent hollow microstructures (3) in the range of 150 nm-210 nm; setting the value range of the length D of the rectangular groove to be 50-80 nm;

selecting the thickness H of the silver film (2) in the range of 40nm to 80nm if the coincidence degree of the target visible light wave band range and the red wave band range is the highest; selecting the center distance P of the adjacent hollow microstructures (3) in the range of 150 nm-210 nm; setting the value range of the length D of the rectangular groove to be 20-40 nm;

step three, in the value range of the rectangular groove length D determined in the step two, taking the maximum value as the rectangular groove length D, and gradually increasing the maximum value; and (3) simulating a transmission spectrum for the optical filter with the current parameters by a finite difference time domain method after each reduction until the simulated result meets the design requirement determined in the step one.

Images